No, combining two versions of SAS in a single Metadata Server will fail to deply. If for some reason it deployed, all of the updates, hotfixes and Web server deployments would fail.
You can combine SAS BI and VA though if they are both the same version and maintenance level, for example SAS BI V9.4M3 and VA 7.3.
However since SAS VA is upgraded more frequently than SAS BI a lot of sites are choosing to install VA separately.
The SAS Users Group for Administrators (SUGA) is open to all SAS administrators and architects who install, update, manage or maintain a SAS deployment.